638 TEXTBOOK OF ZOOLOGY 



demanding more and more furs. The most commonly used and abun- 

 dantly sold furs are in the following order : mole, rabbit, skunk, 

 muskrat, opossum, squirrel, fox, ermine, wallaby, mink, wolf, civet 

 eat, and raccoon. There are several vei*y valuable fur-bearing ani- 

 mals coming very near the point of extinction, and there should be 

 an earnest effort made to restore them. In this group would be in- 

 cluded beaver, fur seal, otter, Russian sable, and chinchilla. A single, 

 choice, silver fox fur may bring a thousand dollars or more, a fisher 

 is valued at about three hundred dollars, the beaver and otter, each 

 at about one hundred ; a wolf is worth about forty as also is the 

 black bear ; the skunk is valued at about six dollars, and the muskrat 

 at about three dollars. Fur farming is being practiced with some 

 species, such as silver fox, mink, muskrat, and rabbits. Rabbit and 

 muskrat farming have the added advantage of producing salable 

 meat. 



Many of the undomesticated mammals become serious pests at 

 times when the usual balance in nature is disturbed. Rats and mice 

 are very destructive of stored provisions, such as fabrics, clothing, 

 grains, and various foodstuffs. These rodents, along with squirrels, 

 gophers, prairie dogs, and groundhogs which normally live on wild 

 plant tubers, seeds, acorns or nuts, are frequently destructive to grain 

 crops. Field mice, rats, and rabbits sometimes damage young fruit 

 trees by gnawing the tender bark just at the surface of the ground 

 until the tree is girdled, thus causing subsequent death. The burrow- 

 ing forms may be killed by fumigating the burrow with carbon di- 

 sulphide, calcium cyanide, or carbon monoxide from the exhaust of 

 an automobile. 



Many of the larger carnivorous mammals are quite destructive of 

 young domesticated animals. The wolf, coyote, fox, and, in some 

 parts of the Southwest, the puma, are quite predatory, killing calves, 

 lambs, kids, and poultry. Certain wild mammals are carriers of 

 disease. In the Rocky Mountain region, ground squirrels and other 

 rodents carry Rocky Mountain spotted fever and transmit it to man 

 through the bite of the spotted fever tick. Bubonic plague is carried 

 by rats and other rodents and is transferred to man by the rat flea. 



The deer and bear are about the only large mammals left that 

 are classified as game animals and hunted for sport. Several others, 

 such as the pronghorn antelope, buffalo, and elk, have been almost 



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